Monday, November 26, 2012

Press Release:

Image by Arne Mooers (SFU),

Gavin Thomas (Sheffield) and Cody Shrank (Yale

A Yale-led scientific team has produced the most
comprehensive family tree for birds connecting all living bird species and
revealing surprising new details about their evolutionary history and its
geographic context.

The researchers relied heavily on fossil and DNA data,
combining them with geographical information to produce the exhaustive family
tree, which includes 9,993 species known to be alive now. Analysis of the
family tree shows when and where birds diversified — and that birds’
diversification rate has increased over the last 50 million years, challenging
the conventional wisdom of biodiversity experts.

“The current
zeitgeist in biodiversity science is that the world can fill up quickly,” says
biologist and co-author Arne Mooers of Simon Fraser University in Canada.
“A new distinctive group, like bumblebees or tunafish, first evolves, and, if
conditions are right, it quickly radiates to produce a large number of
species. These species fill up all the available niches, and then there is
nowhere to go. Extinction catches up, and things begin to slow down or stall. For
birds the pattern is the opposite: Speciation is actually speeding up, not
slowing down.”

The researchers attribute the growing rate of avian
diversity to an abundance of group-specific adaptations. They hypothesize that
the evolution of physical or behavioral innovations in certain groups, combined
with the opening of new habitats, has enabled repeated bursts of
diversification. Another likely factor has been birds’ exceptional mobility,
researchers said, which time and again has allowed them to colonize new regions
and exploit novel ecological opportunities.